Skip Navigation
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

National Institute of Environmental Health Sciences

Use this QR code to view the newest version of this document
Use this QR code to view the newest version of this document

Your Environment. Your Health.

Publication Detail

Title: The Toll-like receptor agonist imiquimod is metabolized by aryl hydrocarbon receptor-regulated cytochrome P450 enzymes in human keratinocytes and mouse liver.

Authors: Mescher, Melina; Tigges, Julia; Rolfes, Katharina M; Shen, Anna L; Yee, Jeremiah S; Vogeley, Christian; Krutmann, Jean; Bradfield, Christopher A; Lang, Dieter; Haarmann-Stemmann, Thomas

Published In Arch Toxicol, (2019 07)

Abstract: The Toll-like receptor 7 agonist imiquimod (IMQ) is an approved drug for the topical treatment of various skin diseases that, in addition, is currently tested in multiple clinical trials for the immunotherapy of various types of cancers. As all of these trials include application of IMQ to the skin and evidence exists that exposure to environmental pollutants, i.e., tobacco smoke, affects its therapeutic efficacy, the current study aims to elucidate the cutaneous metabolism of the drug. Treatment of human keratinocytes with 2.5 µM benzo[a]pyrene (BaP), a tobacco smoke constituent and aryl hydrocarbon receptor (AHR) agonist, for 24 h induced cytochrome P450 (CYP) 1A enzyme activity. The addition of IMQ 30 min prior measurement resulted in a dose-dependent inhibition of CYP1A activity, indicating that IMQ is either a substrate or inhibitor of CYP1A isoforms. Incubation of 21 recombinant human CYP enzymes with 0.5 µM IMQ and subsequent LC-MS analyses, in fact, identified CYP1A1 and CYP1A2 as being predominantly responsible for IMQ metabolism. Accordingly, treatment of keratinocytes with BaP accelerated IMQ clearance and the associated formation of monohydroxylated IMQ metabolites. A co-incubation with 5 µM 7-hydroxyflavone, a potent inhibitor of human CYP1A isoforms, abolished basal as well as BaP-induced IMQ metabolism. Further studies with hepatic microsomes from CD-1 as well as solvent- and β-naphthoflavone-treated CYP1A1/CYP1A2 double knock-out and respective control mice confirmed the critical contribution of CYP1A isoforms to IMQ metabolism. Hence, an exposure to life style-related, dietary, and environmental AHR ligands may affect the pharmacokinetics and, thus, treatment efficacy of IMQ.

PubMed ID: 31111189 Exiting the NIEHS site

MeSH Terms: Adult; Animals; Antineoplastic Agents/administration & dosage; Antineoplastic Agents/metabolism; Cells, Cultured; Chromatography, Liquid; Cytochrome P-450 CYP1A1/genetics; Cytochrome P-450 CYP1A1/metabolism*; Cytochrome P-450 CYP1A2/genetics; Cytochrome P-450 CYP1A2/metabolism*; Dose-Response Relationship, Drug; Female; Humans; Imiquimod/administration & dosage; Imiquimod/metabolism*; Keratinocytes/metabolism*; Male; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Knockout; Microsomes, Liver/metabolism; Middle Aged; Receptors, Aryl Hydrocarbon/metabolism

Back
to Top